The present invention relates to a compact zoom lens having a small lens aperture which projects an image from a light valve such as, mainly, a DMD (Digital Micromirror Device), in which an image is formed by changing reflecting directions of light shone thereon, on to a screen or the like on an enlarged scale.
Adopting a DMD on a projector unit as a light valve is regarded as advantageous over other methods in obtaining miniaturized projector units. Currently, portable compact projector units have been broadly propagated, and among them, data projectors constitute a center of interest because of its handiness when presenting information. In projector units designed to be portable, it is critical to reduce the thickness of a projector unit, and hence, it can be said that the reduction in thicknesses a most critical factor in projector units which are in many cases carried together with a note-type personal computer for use in combination therewith. As an example of a means for solving this problem, for example, the Japanese Unexamined Patent Publication No. 2004-271668 discloses, a design method for making compact a projection lens.
An aspect of the invention is to provide a projector unit which is thin enough to be carried conveniently and which can project an enlarged image with high image quality on to a large screen even within a limited space by realizing a compact zoom lens.